Biology: The Science of Exceptions

[Edit: March, 2018. Every year, I get a large number of visitors from Nepal and Bhutan on this post. Welcome, everyone. I’m just curious why this seems to happen every year at the same time. Could someone please let me know? It would help me understand how this site is being used, particularly if it’s for educational purposes. Thank you.]

Biology is sometimes referred to as “the science of exceptions.” A few recently reported examples from the study of animal behavior (i.e., ethology) help to bolster that reputation.

The first instance has probably received the most attention simply because it’s just so cool. It’s a video from Russia of some type of wild corvid (others have said it is most likely a hooded crow) that appears to snowboard down a roof. It does this multiple times by sliding on a small unidentified object under its feet, picking it up with its beak when it gets to the bottom of the roof, then flying back to the top to do it again. See for yourself.

Jason Goldman at Scientific American has written that while it’s tempting to infer that this represents an act of play, that there is the danger of anthropomorphizing and seeing this behavior through a human lens. He also notes that while this behavior is anecdotal, the literature on wild corvids from various locations shows that they have been observed to engage in other behaviors reminiscent of play, including sliding down snowy inclines. While snowboarding and sliding may not be a part of the regular repertoire of corvid behavior, it is not a complete aberration either.  Rather, they demonstrate great behavioral flexibility and remarkable intelligence, including improvising to make tools to obtain fooddropping nuts in traffic to crack them open (and waiting for the traffic light), and recognizing individual human faces.

Example number two comes from wild Sumatran orangutans who have been seen eating meat (a slow loris). Orangutans are primarily frugivorous, though apparently there are a few other reported observations in the literature of meat-eating. Therefore, this behavior appears to be exceedingly rare, but as with crows ‘snowboarding,’ it is not completely novel.

The final example concerns another of our closest relatives, and a rare episode of violence in bonobos, who are usually quite peaceful apes. According to Barbara J. King, an anthropologist at William and Mary: “This anecdote brings the forest apes to life in a startling way and shows that there is no single way to be a bonobo. Generalizing about the behaviour of apes is an exercise doomed to failure, because variation across populations and individuals is marked.”

The three examples above show that animal behavior is quite complex, and leaves lots of room for individual variation. If there is no single way of being a bonobo, then there is no single way of being a human either. What is ‘normal’ is a matter of statistical abstraction.

The legendary biologist Ernst Mayr (1976) argued that one of the reasons evolution has been opposed historically (aside from religion) is that we have a strong tendency to think in typological either/or categories, including for species. A byproduct of this tendency to want to put things into neat boxes (conservative or liberal, fish or reptile, etc.) is that we downplay or overlook variation and complexity.  In his terms, most laypeople are typological thinkers, while biologists are forced to be “population thinkers.” 

The assumptions of population thinking are diametrically opposed to those of the typologist. The populationist stresses the uniqueness of everything in the organic world. What is true for the human species, that no two individuals are alike, is equally true for all other species of animals and plants… All organisms and organic phenomena are composed of unique features and can be described collectively only in statistical terms. Individuals, or any kind of organic entities, form populations of which we can determine the arithmetic mean and the statistics of variation. Averages are merely statistical abstractions; only the individuals of which the populations are composed have reality. The ultimate conclusions of the population thinker and  of the typologist are precisely the opposite. For the typologist, the type (eidos) is real and the variation an illusion, while for the populationist the type (average) is an abstraction and only the variation is real. No two ways of looking at nature could be more different.” 

In a given population, there may be clear trends in terms of genes, anatomy, and behaviors. However, we must also avoid the temptation to zoom out too far and miss the individual trees while focusing solely on the forest. 


Mayr E. 1976. Typological versus population thinking. In: Mayr, E. (ed.). Evolution and the diversity of life: selected essays. Cambridge, Mass.: Belknap Press, Harvard University Press, p. 26-29.

12 thoughts on “Biology: The Science of Exceptions

  1. A couple more thoughts:

    1) Another of Mayr’s points about typological thinking was that some people have trouble thinking in evolutionary terms because they cannot fathom intermediates since that would defy the essence (eidos) of a category. Not only does the typological thinker overlook variation within a category, but also possible fluidity between them. Many creationists, for example, have said that they have trouble conceptualizing macroevolution and intermediate species because they’ve never seen a half-cow/ half-whale, or a half-monkey/half-human. Or a croco-duck. Those hybrids would go against ‘cowness’ or ‘whaleness.’ It’s a mental block set up by typological thinking.

    2) There are lots of other ‘aberrational’ behaviors in wild animals out there that I could have included: chimpanzees who play in water, gorillas using tools, octopuses using coconut shells for protection, etc.

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